Long-lasting ice packs that stay cold for 36 hours and what you can to do further extend its cooling capacity

Post In: Cooling Ice Packs
Long-lasting ice packs that stay cold for 36 hours and what you can to do further extend its cooling capacity

Keeping your meals fresh while you’re in school, traveling or just out having fun is a challenge. Thank goodness for lunch bags and coolers that keep your perishables fresh until you’re ready to consume them! 

Besides these handy food preservers, ice packs for coolers and lunch bags keep your foods and beverages in safe temperatures while you’re camping, spending time on the beach, having a picnic or simply packing your lunch for school or workplace.   

If you’re curious to know some food safety considerations, how coolers and lunch bags keep your food cold and how long these ice packs last in your cooler and lunch bags, please read on.    

Why do I need to keep food cold?

The general rule for food preservation is simple. Keep hot foods warm and cold foods chilled. The US Agriculture recommends hot foods should be kept at 140 degrees Fahrenheit (60 degrees Celsius) or above, while cold foods should be stored at 40 degrees Fahrenheit (4.4 degrees Celsius).

Perishable foods are vulnerable to microorganisms and bacteria that are present everywhere – in the air, water, soil and even in the food we eat. Bacteria thrive in environments suitable for their reproduction, with moisture, time and temperature, being the main factors for bacterial proliferation. 

Freezing or chilling your food is important as it minimizes the movement of molecules, temporarily putting bacteria at a standstill, too. However, once the temperature increases, bacteria reactivate and multiply exponentially. 

What is the temperature danger zone?

The “temperature danger zone” refers to the temperature in which the bacteria that trigger food poisoning proliferate. It is pegged between 40–140 degrees Fahrenheit (4.4–60 degrees Celsius). Within the said temperature range, bacterial growth is fastest between 70–125 degrees Fahrenheit (21–51 degrees Celsius).  

As a result, consumables that are stored and handled without a cooling source will get spoiled or become unfit for consumption after several hours. 

How long can cold food stay at room temperatures?

The US Food and Drug Administration (FDA) recommends the two-hour rule, suggesting you should not keep foods that require refrigeration to stay at room temperatures for more than two hours (or one hour if the ambient air temperature is above 90 degrees Fahrenheit, 32 Celsius). Warmer temperatures encourage bacteria to multiply faster, thus, it is vital to heat or freeze the food back to safe temperatures as soon as possible.

What is the 2-hour and 4-hour rule on food safety?

Those in the food industry follow the 2-hour and 4-hour rule, the basis being the time when the food was taken out of the refrigerator. In general, meals stored between 5-60 degrees Celsius (40-140 Fahrenheit) for less than two hours can be used or put back in the refrigerator to use later. 

If kept in the same temperature for more than two hours to a maximum of four hours, it should not be placed back in the fridge. If food sits in the said temperature range for more than four hours, it should be thrown away. 

How long can a lunch box or cooler keep food and drinks cold?

There’s no definitive answer to this one. Industry estimates indicate that insulator-lined lunch bags are capable of keeping warm food for two to three hours and cold meals for up to four hours, on average. This essentially coincides with the FDA’s two-hour rule to avoid bacterial growth. 

It is worth mentioning that this average lunch box cooling time is impacted by a few factors, among them being the type of insulation used as well as the ambient temperature. 

When ice packs are placed in insulated lunch bags, your consumables can stay cold for up to four hours more, making ice packs essential in your child’s lunch box or bag.  

Coolers can keep food fresh for up to one week, as long as you keep the cooler’s temperature at 40 degrees Fahrenheit (4 degrees Celsius) or below with the help of these cooler buddies. At room temperature, coolers only last for three to four hours. 

How long do gel ice packs last inside a lunch box or cooler?

Choosing the best cooler and lunch bag is key to keeping your food and beverages fresh for a long time. Go for one that’s designed to shut out heat and keep the coldness in for an extended period. 

Gel ice packs can help enhance and extend the cooling life of lunch bags and coolers. For instance, these high quality lunch box ice packs are lightweight and compact but powerful enough to keep your foods fresh and crisp for up to eight hours. 

When placed in a cooler, gel-based ice packs last anywhere from 12–36 hours. This 6-set long-lasting cooling ice packs, however, edges out the competition by being able to stay cold the longest. With its freezing temperature pegged at 18 degree Fahrenheit (-8 Celsius), these cooling packs stay cooler than regular ice and other water-based coolants, which freeze at 32 degrees Fahrenheit (0 Celsius) and melt easily. 

Additionally, because this set includes three pieces of large (25×10”) and small (4.7x 4.7”) packs, you’re able to cool your food in a variety of lunch bag or cooler sizes.

How to keep cold meals chilled at home 

It is best to keep foods chilled to prevent foodborne illnesses. The FDA further advises to keep the refrigerator at 40 degrees Fahrenheit (4 Celsius) or below, and the freezer at  0 Fahrenheit (-18 Celsius) to reduce the risk of bacterial growth or proliferation in our food. Using an appliance thermometer will help you ensure the proper temperature is set at all times. 

Foods kept in proper (cold) temperatures prevent or slow down the growth of several bacteria, among them listeria, e. coli and salmonella, that can make us sick. 

This is not to say, though, that foods kept in the fridge are completely safe and immune from bacterial growth. Don’t be surprised if, after several days, that sandwich you mindlessly tucked inside the fridge will smell funny and develop molds.  

How to keep cold meals chilled outside of home 

These tips will show you how to chill when things get heated up in the great outdoors. 

  • Freeze your food or drinks before placing them in your lunch box or cooler. 
  • Pre-chill your cooler or lunch box. 
  • Have at least two pieces of cooling sources. For instance, use at least two gel packs in your lunch bag or box or a cooling pack. For your cooler, use regular ice, ice packs and frozen bottled waters to keep perishables fresher for longer.  
  • Line your cooler with an aluminum insulator to retain temperature for a bit longer.
  • Cover the top with a thin foam sheet, a yoga mat or a woolen blanket to let cold air stay in your cooler and for the warm air to keep out. 
  • Use big blocks of ice because they melt slower than ice cubes.

Where do I place the ice packs for long lasting coldness?

If you have a few consumables mixed inside your lunch bag, prioritize and place the ice packs close to foods that need to be chilled. It’s completely okay not to put cold packs near fruits, vegetables, chips and dips, for instance. 

To maximize cooling time, put one gel pack on the bottom and another one on the top of your lunch box. 

If you’ve got plenty to spare, make sure to place flexible ice packs in all the vacant spaces in your lunch box to reduce the chances of warm air from circulating inside. This advice goes to your cooler boxes, too.

For coolers, line a block of ice at the bottom. Place foods that need to be fresh for the longest, such as meat and similar food types. Add another layer of ice and place dairy products like butter on top of it. Arrange the most frequently consumed foods at the top.  

Here’s a quick tip: using a pre-chilled cooler buddy with frozen food allows you to have an even longer cooling time for your cooler or lunch box. 

How does a cooler or a lunch box work? 

Coolers and lunch bags rely on insulation and ice to keep things cold. Insulation slows down the convection process, which happens when the hot air moving around an enclosed space increases the internal temperature. 

This reduction in convection rate helps prevent another related process from happening: conduction. Conduction, which occurs when a warm object transfers heat to a nearby object, is also temporarily suspended thanks to the insulation inside your lunch box and coolers.  

Add ice pack coolers in the equation, and voila, you get that lasting, chilling effect on your perishables. 

Keep the cooler or lunch box lid closed to avoid these processes. Each time you open the cover, you’ll invite warm air to spark the convection process, increasing the temperature slightly. 


Proper food handling is a key factor in preventing common foodborne illnesses caused mainly by bacteria. Keeping lunches and beverages cold is a challenge when you’re outside your home.   

Knowing the safe and dangerous temperatures for microorganisms to multiply gives us another reason to get serious in food handling and safety. Invest in proper food storage tools outside your home such as lunch bags, coolers and ice packs to keep your perishables safe. 

How long does your food stay cold in your lunch box or cooler? What extra steps do you take to make them last longer? Tell us more about it in the comments section or contact us here.

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